Complement cascade

Reviewed: D'Eustachio, P, 2006-07-03 21:35:13 Edited: Jupe, S, 2010-11-11 The complement system is a biochemical cascade, so named because it 'complements' the ability of antibodies to clear pathogens. It is part of the innate immune system. Complement system proteins circulate in the blood as inactive precursors (pro-proteins). When triggered by the presence of microbes, complement proteases cleave complement proteins, initiating a cascade of further cleavages. The end-result of this activation is the activation of the Membrane Attack Complex and cell lysis. The C3 and C5 components also lead to phagocytosis by leukocytes.<br><br>There are three branches that lead to activation of the complement system: the classical complement pathway, the alternative complement pathway, and the mannose-binding lectin pathway. Complement proteins are always present in the blood and a small percentage spontaneously activate. Innapropriate activation leads to host cell damage, so the activation process is tightly controlled by several regulatory mechanisms. N.B. Originally the larger fragment of Complement Factor 2 (C2) was designated C2a. However, complement scientists decided that the smaller of all C fragments should be designated with an 'a', the larger with a 'b', changing the nomenclature for C2. Recent literature may use the updated nomenclature and refer to the larger C2 fragment as C2b, and refer to the classical C3 convertase as C4bC2b. Throughout this pathway Reactome adheres to the original convention to agree with the current (Feb 2012) Uniprot names for C2 fragments. Authored: de Bono, B, 2004-08-04 09:17:50

http://purl.obolibrary.org/obo/HINO_0022320

Reviewed: D'Eustachio, P, 2006-07-03 21:35:13

Edited: Jupe, S, 2010-11-11

The complement system is a biochemical cascade, so named because it 'complements' the ability of antibodies to clear pathogens. It is part of the innate immune system. Complement system proteins circulate in the blood as inactive precursors (pro-proteins). When triggered by the presence of microbes, complement proteases cleave complement proteins, initiating a cascade of further cleavages. The end-result of this activation is the activation of the Membrane Attack Complex and cell lysis. The C3 and C5 components also lead to phagocytosis by leukocytes.

There are three branches that lead to activation of the complement system: the classical complement pathway, the alternative complement pathway, and the mannose-binding lectin pathway. Complement proteins are always present in the blood and a small percentage spontaneously activate. Innapropriate activation leads to host cell damage, so the activation process is tightly controlled by several regulatory mechanisms. N.B. Originally the larger fragment of Complement Factor 2 (C2) was designated C2a. However, complement scientists decided that the smaller of all C fragments should be designated with an 'a', the larger with a 'b', changing the nomenclature for C2. Recent literature may use the updated nomenclature and refer to the larger C2 fragment as C2b, and refer to the classical C3 convertase as C4bC2b. Throughout this pathway Reactome adheres to the original convention to agree with the current (Feb 2012) Uniprot names for C2 fragments.

Authored: de Bono, B, 2004-08-04 09:17:50

Pubmed14698228

ISBN0781735149

Reactome, http://www.reactome.org

Pubmed11044372

Pubmed3052276

Pubmed11213801

Pubmed15476920

Complement cascade

http://purl.obolibrary.org/obo/NCBITaxon_9606

HINO:0022320

Complement cascade

Reactome Database ID Release 43166658

ReactomeREACT_6932

http://purl.obolibrary.org/obo/INO_0000021

http://purl.obolibrary.org/obo/HINO_0022299

http://purl.obolibrary.org/obo/HINO_0022300

http://purl.obolibrary.org/obo/HINO_0022321

http://purl.obolibrary.org/obo/HINO_0022289